Photo process for preparing mixtures with building tack which are based on rubber-like copolymers of ethylene

ABSTRACT

A process for preparing a mixture based on a rubberlike copolymer of ethylene, at least one other alpha - alkene and one or more polyenes and tackifying resins which has good building tack. 
     This good building tack can be obtained if the copolymer contains C═C bonds positioned in the non linear part of the polymer chains, the carbon atoms of which C═C bonds either have two hydrocarbon groups which are in vicinal cis relative positions and which do not form part of the same cyclic system, or have at least three hydrocarbon groups. In order to obtain the desired high building tack value the mixture must show in unvulcanized state an elongation at break of at least 500% and a tensile strength lying between 1.5 and 50 kg/cm 2 . The mixture must be subjected to an artificial light source radiating light with a wave length of between 200 and 300 nm and impacting a radiated energy to the mixture of at least 2 microwatts/cm 2  per nm in the presence of oxygen and a photosensitizer.

This application is a continuation-in-part of Ser. No. 517,052, filedOct. 22, 1974, now abandoned.

The invention relates to a process for preparing mixtures with buildingtack which are based on a rubber-like copolymer of ethylene, at leastone other alpha-alkene, and one or more polyenes and tackifying resins.

Amongst the synthetic rubber-like polymers known those composed ofethylene, at least one other alpha-alkene, and one or more polyenes takean important place because of their excellent resistance to ozone,weather influences, and ageing. These favourable properties make itattractive to apply copolymers of this kind for a variety of purposes.

However, copolymers composed of ethylene, at least one otheralpha-alkene, and one or more polyenes, as is the case with manysynthetic elastomers, like styrenebutadiene copolymers, have little orno tack or building tack.

Building tack or tack is here understood to mean the bonding strengthwhich surfaces of the same non-vulcanized rubber show towards each otherif contacted at a moderate pressure.

A sufficiently large tack, however, is necessary for the manufacture ofmany objects and in particular for the manufacture of objects built upof several parts or layers, like driving belts, conveyor belts, and moreparticularly motor-tires. For, by means of an adequate tack apermanently good bond between the various parts or layers of which thearticle is made is obtained during the assembly and the vulcanization.

In the case of the rubber-like copolymers of ethylene, at least oneother alpha-alkene, and one or more polyenes, a solution for the tackdeficiency has been sought in methods according to which objects aremanufactured by separately cementing each of the rubber surfacestogether to a sandwich-like structure with the aid of an adhesive whichis applied in layers. Such a process is not only cumbersome and, hence,not attractive for industrial application, but in the composition andapplication of adhesives of this kind flammable organic solvents areapplied as a rule, so that such a method, if for no other reason butoperational safety, is not advisable.

Another possibility for the elimination of the tack deficiency of thesecopolymers which are composed of ethylene, at least one otheralpha-alkene, and one or more polyenes is admixture of elastomers havingsufficient tack as such. It has notably been investigated whetheradmixture of natural rubber would offer a solution. It has appeared,however, that such large quantities of natural rubber have to be admixedto obtain a mixture having an acceptable tack level that the resistanceagainst ozone and ageing is strongly reduced. In this way, the advantageinvolved in using copolymers of ethylene, at least one otheralpha-alkene, and one or more polyenes are lost to a considerabledegree. Moreover it has appeared that the physical and mechanicalproperties of these mixtures after vulcanization are appreciably lessthan those of the polymers separately.

Also numerous tackifying resins, so-called tackifiers, have beendeveloped, like condensation products of phenols and aldehydes andcondensation products of acetylene, alkylated phenol resins, such asthose known by the trade mark of Amberol ST 140 F, phenolated isopreneresins and phenolated isoprene copolymer resins. These resins offer theadvantage that they can be mixed through the whole rubber mass and neednot be applied to the rubber faces in layers. In practice, however, ithas appeared necessary, in order to achieve a tack level which isreasonable in some degree, to add tackifiers in such large quantitiesthat this results in a deterioration of the properties of the vulcanizedproduct. Moreover, these tackifiers migrate strongly to the rubbersurface owing to the application of these large quantities, so-calledsweating. In the rolled and calandered rubber-like ethylene copolymersthere is a risk, because of the application of these large quantities,that during storage the excessive sweating will fully undo the usefuleffect initially achieved and even change it into a disadvantageouseffect. Further, the use of such large quantities of tackifier isextremely expensive. If the tackifier is applied in minor amounts, thesedisadvantageous phenomena are largely avoided; unfortunately, however, asatisfactory bonding strength has never been achieved in practice withapplication of such amounts.

These experiences, supported by numerous experiments with a greatvariety of tackifiers and rubber-like ethylene copolymers, therefore,have led those skilled in the art to believe that the tack ofrubber-like ethylene copolymers cannot be so increased by admixture oftackifiers that compositions based on ethylene copolymers and tackifiersare obtained which have a satisfactory bonding strength.

From the Netherlands patent application Nos. 7113143 and 7113144 it isknown that mixtures consisting of rubber-like copolymers of ethylene, atleast one other α-alkene, and one or more polyenes, together with one ormore tackifiers, have an unprecedentedly good bonding strength if thethermogram recorded by means of differential scanning calorimetry, inwhich thermogram the heat of crystallization is plotted as a function ofthe temperature, shows a peak (d.s.c. peak) whose maximum lies at atemperature of between -7° and 11° C. In this process the mixture ofrubber-like ethylene copolymer, tackifier, and, possibly, the usualadditives is stored for many hours, whereupon the desired bondingstrength is obtained. Such a process however is not attractive inpractice because of the long storage time. If the mixture is stored fora shorter time the bonding strength obtained will usually be lower.Additionally, the bonding strength value is subject to undesirablevariations.

The purpose of the invention is to provide a process which, in a rapidand surer way, yields compositions with such a large and constantbonding strength that they can be applied with optimum results for themanufacture of various objects, particularly such built up from severallayers articles as driving belts, conveyor belts, and, principally,motor-tires.

It has now been found that in case the ethylene copolymer contains C═Cbonds in the non-linear part of the polymer chains, the carbon atoms ofwhich bonds either having two hydrocarbon groups which are in vicinalcis relative positions and which do not form part of the same cyclicsystem or having at least three hydrocarbon groups, a very high andconstant bonding strength can be obtained within a very short period oftime provided the mixture of ethylene copolymer, tackifying resin, and,possibly, the usual additives is exposed to light having a wave lengthof between 200 and 800 nanometers in the presence of oxygen and aphotosensitizer and the mixture, in non-vulcanized state, has anelongation at break of at least 500% and a tensile strength lyingbetween 1.5 and 50 kg/cm².

It was extremely surprising that with the aid of light, moreparticularly with light imparting a great radiated energy to themixture, together with a photosensitizer in the presence of oxygen,constant and high bonding strength values could be reached in a veryshort period of time which, previously, were not possible or onlypossible after a long storage period provided the mixture has highlyspecific mechanical properties. By preference, light is applied whichimparts to the mixture a radiated energy of at least 2 μW/cm² pernanometer.

Although already in the Netherlands Patent Applications mentioned aboveethylene copolymers were applied which, in the non-linear part of thepolymer chains, contained C═C bonds whose carbon atoms had threehydrocarbon groups, and the mixtures of these copolymers, together withtackifying resin and the usual additives, such as carbon black and oil,have, of course, been subjected to normal room light, this light hasnever had a larger intensity than that of the normal fluorescence lampsused for illumination of room, notably 0.8 μW/cm² per nanometer. In thepresent process, preferably, radiated energies are applied in excess of30, more particularly in excess of 200 μW/cm² per nanometer.

It was known from the Netherlands patent application No. 6,900,810 thatto mixtures of ethylene copolymer, tackifying resins, and the usualadditives, bonding strength can be imparted by ageing said mixtures andby subsequently exposing them to ultraviolet light filtered throughnormal window glass. In this Application only one ethylene copolymer isdescribed whose carbon atoms of the C═C bonds positioned in thenon-linear part of the polymer chains have three hydrocarbon groups, twoof which hydrocarbon groups, which have a geminal relative coupling tothese C═C bonds, form part of a cyclic system, notably anethylene-propylene-ethylidene-norbornene terpolymer. However, a mixturein which said ethylene copolymer is incorporated, together with atackifying resin and the usual additives, and which, for a day or for aweek, has been exposed to UV-light supplied by indirect, bright sunlightfiltered through window glass, shows to have a small bonding strength.This is to be attributed, amongst others, to the circumstance that thisethylene copolymer -- as established by Applicant -- cannot show anelongation at break of more than 500%. Nor has a photosensitzer beenapplied, in the absence of which only low bonding strength values can bereached. Nothing at all is mentioned about the tensile strength.

It is highly surprising that mixtures based on ethylene copolymers whichhave highly specific properties as regards elongation at break andtensile strength and which at the same time satisfy special demands madein relation to the structure of the C═C bonds in the side-chains can, ina rapid and efficient manner, be given bonding strength with the aid ofa photosensitizer and light in the presence of oxygen.

It has further been found that the use of visible light is to bepreferred to UV-light. Therefore, the artificial light source should, atleast at a wave length from the visible light, preferably at a wavelength smaller than 600 nm, impart a radiated energy to the mixture ofat least 2, by preference at least 30, and more particularly at least200 microwatts/cm² per nm. Although, therefore, visible light ispreferred, UV-light may be tolerated in a minor quantity. This appliesin particular to UV-light having a wave length in excess of 360 nm. Theamount of UV-light to be admitted will depend on the required bondingstrength value. For optimum bonding strength values UV-light will,preferably, be avoided as much as possible. Therefore, the totalquantity of radiated energy from the UV-light between 200 and 400 nmamounts by preference to at most half, more particularly to at most afourth part of the total received quantity of radiated energy of thelight in the wave length range from 200 to 600 nm.

It has appeared that not only UV-light below 325 nm (which light isstopped by normal window glass) has a detrimental influence on the tack,but that also UV-light between 325 and 400 nm is detrimental to the tackvalue to be achieved and to the speed at which said value is reached.For this reason the total quantity of received radiated energy byUV-light with a wave length between 325 and 400 nm amounts, preferably,to at most a fourth part, more particularly to at most a sixth part, ofthe total quantity of received radiated energy of the light in the wavelength range from 325 to 600 nm.

It has also been found that there is a maximum as regards the allowablequantity of radiated energy to which the surface of the mixture may beexposed. For instance, it has been established that the bonding strengthis quite absent if the mixture, when exposed to light having a wavelength of between 200 and 800 nanometers, has received a total radiatedenergy of more than 15 Joules/cm² per nanometer.

Generally, the time of exposure chosen will have to be so short that thetotal quantity of radiated energy received is smaller than 5 Joules/cm²per nanometer, since the bonding strength already decreases perceptiblythen. For reasons of economy a total irradiation energy of less than 2is chosen, more particularly of less than 1 Joule/cm² per nanometer,because already at this irradiation energy a maximum bonding strength isreached and further exposure does not yield an improvement and,ultimately, will even lead to a decrease or complete disappearance ofthe bonding strength.

The exposure may be effected at widely divergent temperatures, forinstance from -50° to +150° C., although, by preference, temperaturesabove 0° C. are applied. It has been found that at an elevatedtemperature the time during which a satisfactory bonding strength isreached can be appreciably reduced. Preferably, therefore, temperaturesare applied which are higher than 35° C., more particularly higher than50° C.

The maximum temperature, though not limited in principle, is chosen tobe less than 150° C. for practical reasons, more particularly less than135° C. At higher temperatures it is necessary, if vulcanizing agentshave been incorporated in the mixture, that the mixture be cooledrapidly to avoid premature vulcanization.

The light sources that may be applied in the process of the inventionare not limited. Examples of applicable light sources are, amongstothers, sodium lamps, mercury vapour lamps, halogen lamps, fluorescencelamps, xenon lamps, mercury iodide lamps, and incandescent lamps.

If required, the light from these light sources may be filtered to limitthe amount of UV-light emitted and keep it within the limits desired.

Of course, the light sources should be so chosen that they are capableof imparting the required, minimum amount of radiated energy to themixture, for which purpose use can be made of the known appliances toconcentrate light, such as reflectors and lenses.

The photosensitizers that may be applied in the process of thisinvention are numerous. Many divergent kinds of photosensitizers may beapplied, like porphyrins, more particularly the porphyrins substitutedwith aromatic groups, such as tetraphenylporphyrin and meso-naphthylsubstituted porphyrins; further, porphyrazines, phthalocyanins,chlorophyl, eosin, methylene blue, methyl violet, fluorescein, hemin,rubrene, acridine, Rose Bengal, and alkyl- and/or aryl-substitutedanthracene, tetracene, pentacene, hexacene and haptacene. In general,polynuclear, aromatic compounds, such as rubrene and the substitutionproducts of, for instance, anthracene, naphthacene, benzanthracene anddiphenylanthracene, are to be preferred because they are readilyavailable in the form of crude oil fractions rich in aromatics. Moreparticularly, these photosensitizers contain 3 to 100, particularly 3 to50 aromatic nuclei, which may be substituted, if necessary. Especiallythe lower-molecular compounds with 3-5 aromatic nuclei should besubstituted by alkyl- and/or, preferably, aryl-groups. The sensitizersknown for UV-light, like benzophenone, cannot be used in the presentprocess.

The effectiveness of the photosensitizers may be strongly different anddepends also on the wave length of the light used. In order to achieveoptimum results the photosensitizer applied and the light source usedwill have to be harmonized.

The amount of sensitizer may vary within wide limits depending on theeffectiveness of the sensitizer and of the light source used, but,generally, small quantities will suffice, for instance between 0.001 and1% by weight, particularly between 0.01 and 0.5% by weight, referred tothe weight of the polymer used. If a photosensitizer is used having avery low effectiveness, more than 1% by weight may be applied, ofcourse, for instance 5% by weight.

The photosensitizer may be applied in different ways. Thephotosensitizer may be incorporated in one of the components of themixture prior to the ultimate mixture being prepared, or a so-calledmasterbatch process may be applied by extending a mixture -- in whichthe photosensitizer is present in a concentrated form -- with a mixturein which it is not present. Although admixture in the rubber mixture isstrongly preferred, the photosensitizer may also be applied at thesurface of the mixture, for instance as a solution in a solvent.

Also two or more photosensitizers may be applied to advantage, toachieve a larger efficiency of the light source. These sensitizers maybe applied as a mixture, but they may also be admixed separately.

The greatest preference is for the use of extender oils for rubberalready containing one or more photosensitizers. In such a case additionof extra photosensitizers is not necessary. For instance, aromatic oilsmay be applied in which polynuclear, aromatic hydrocarbons are alreadypresent which may act as photosensitizer. Preferably, therefore,aromatic oils are applied which do not show complete transmission atwave lengths greater than 400 nm. By preference, the transmission issmaller than 95%, more particularly smaller than 80% measured at 400 nmin a solution of 74 mg of oil in 100 ml of n-hexane in a 1-cm cuvette.

Applicant assumes -- though he does not wish to bind himself to this --that photochemical oxidation of a surface takes place if the surface isirradiated with the proper light in the presence of oxygen and aphotosensitizer. Said photochemical oxidation is effected by the actionof singlet oxygen -- formed from triplet oxygen -- on the highlyspecific unsaturation which is built into the side-chains of thecopolymers and which is no longer present after the vulcanization. Thisis in contrast with an auto-oxidation which proceeds via a radicalmechanism and is not selective, like an oxidation with, for instance,ozone and/or ultraviolet light in the presence of oxygen and, possibly,in the presence of an oxidation catalyst, in which decomposition of thepolymer surface cannot be avoided.

The rubber-like ethylene copolymer should contain C═C bonds positionedin the non-linear part of the polymer chains, the carbon atoms of whichbonds either have two hydrocarbon groups which are in vicinal cisrelative positions and which do not form part of the same cyclic system,or, and preferably, have at least three hydrocarbon groups.

It is quite clear that at least one of the hydrocarbon groups of the C═Cbonds should form a link with at least one carbon atom of the polymerchain. In that case the hydrocarbon group is considered to include tothe carbon atom of the linear part of the polymer chain, the so-calledback-bone. The polymers applicable according to the invention are thosepolymers whose C═C bonds either have two hydrocarbon groups which are invicinal cis relative positions and which, together, do not form part ofthe same cyclic system, or, and preferably, have at least threehydrocarbon groups. With, for instance, a copolymer of ethylene,propylene, and dicyclopentadiene these conditions are not satisfied andonly a small bonding strength is obtained with application of theprocess according to the invention, in that case. This also applies tocopolymers of ethylene, propylene, and hexadiene 1,4, in which thehexadiene 1,4 is present in the polymer in the trans configuration.

If a polymer is applied whose C═C bonds have two hydrocarbon groupswhich are in vicinal cis relative positions and which, together, do notform part of the same cyclic system, the hydrocarbon groups may be anaryl-, an aralkyl-, an alkaryl-, a cycloalkyl- or an alkyl-group,preferably with 1-18 carbon atoms and more particularly 1-8 carbonatoms. Examples of polymers having such C═C bonds are those polymers inwhich hexadiene-1,4, 6-methylheptadiene-1,4,1-vinyl-4-(propenyl-1)-cyclohexane, 6-phenylhexadiene-1,4,3-isopropylhexadiene-1,4, and 4(1-butenyl-2)-styrene are incorporated.These monomers must be present in the polymer in the cis configuration.If the C═C bonds contain at least three hydrocarbon groups, which ispreferred, said hydrocarbon groups may consist of an alkyl-, acycloalkyl-, an aryl-, an alkaryl- or an aralkyl-group with, preferably,1-18 carbon atoms and more particularly 1-8 carbon atoms. Examples ofpolymers of such unsaturation are those polymers in which the followingcompounds are incorporated: 5-methylhexadiene-1,4;4-ethyl-hexadiene-1,4; 4-isopropyl-hexadiene-1,4;4,5-dimethylhexadiene-1,4; 5-methyloctadiene-1,5; 6-methyloctadiene-1,5;6-methylheptadiene-1,5; 5,7-dimethyloctadiene-1,5;4,5-dipropyloctadiene-1,4; 5-propyl-6-methylheptadiene-1,5;6-phenyl-4-propylhexadiene-1,4; 5-ethyl-7-methyl-octadiene-1,6, and4-(2-buten-2-yl)-styrene. If the C═C bonds located outside the linearpart of the polymer chains contain three or more hydrocarbon groups,also two hydrocarbons which are linked up with these C═C bonds ingeminal relative, or in vicinal relative, positions may form part ofcyclic systems. Examples of cyclic systems of this kind are thecyclo-octene system, the bicyclo(2,2,1)-heptene system, thebicyclo(2,2,2)-octene system, the dicyclopentadiene system, thetetra-hydro-indene system, the bicyclo(4,4,0)-decadiene system, thebicyclo(3,2,0)-heptene system, and the bicyclo(3,3,0)-octadiene system.

Examples of polymers with this type of cyclic systems are those polymersin which the following monomers are incorporated:4-methylcyclo-octadiene-1,4; 4-methyl-5-propylcyclo-octadiene-1,4;5-ethylidenenorbornene-2; 5-propylidenenorbornene-2;5-butylidenenorbornene-2; 5-isopropylidene-norbornene-2; further,2-methylnorbornadiene-2,5; 2-propyl-norbornadiene-2,5;3-heptylnorbornadiene-2,5; 2-ethyl-3-propylnorbornadiene-2,5; and2-(1',5'-dimethylhexen-4-yl)norbornadiene-2,5; further,5-isopropylidene-bicyclo(2,2,2)octene-2;5-ethylidenebicyclo(2,2,2)octene-2; 5-butylene-bicyclo(2,2,2)octene-2;further, 2-ethylbicyclo(2,2,2)octadiene-2,5;2-methyl-3-ethylbicyclo(2,2,2)octadiene-2,5;2-hexylbicyclo(2,2,2)octadiene-2,5, and2-(1',5'-dimethylhexenyl-4)bicyclo(2,2,2)octadiene-2,5; further,5-methyldicyclopentadiene; 4-methyl-5-ethyldicyclopentadiene, and5-isopropyldicyclopentadiene; further,3-methyl-4,7,8,9-tetrahydroindene; 2-propyl-4,7,8,9-tetrahydro-indene;further, 1-isopropylidene-4,7,8,9-tetrahydro-indene;1-(1'-phenyl)ethylidene; 4,7,8,9-tetrahydro-indene; further,1-isopropylidene-bicyclo(4,4,0)decadiene-2,6;2-isopropylidene-bicyclo(4,4,0)decene-6, and2-ethylidenebicyclo(4,4,0)decene-6; further, 3-ethylenebicyclo(3,2,0)-heptadiene-2,6, and 3-methylbicyclo(3,3,0)-octadiene-2,6.

The quantity of polyene incorporated in the copolymers according to theinvention may vary within wide limits, preferably, however, a quantityof 0.1 to 20% by weight is applied.

It is self-evident that the polyenes which do not yield the required C═Cbond structure in the side-chains during copolymerization are littlerelevant as regards reaching good tack values and that these unsaturatedC═C bonds as such do not affect the bonding strength.

The polyenes that do yield the required structure are, by preference,applied in a quantity greater than 0.5% by weight, in particular greaterthan 1% by weight and smaller than 10% by weight. The best tack valuesare obtained with quantities in excess of 3% by weight.

The ethylene copolymers applicable according to the invention can ingeneral be prepared by interpolymerization of a mixture of ethylene, atleast one other alpha-alkene, and, possibly, one or more polyenesdissolved in an organic solvent whether or not containing halogen, orsuspended, with the aid of a coordination catalyst.

For the coordination catalyst a catalyst may be applied which has beenformed by combining at least one compound of a metal of the side-groups4 up to and including 6 or 8 of the periodic system according toMendelyeev, including thorium and uranium, the so-called heavy-metalcomponent, with a metal, an alloy, a metal hydride or a metal compoundof a metal of the groups 1 up to and including 3 or of the fourth maingroup of this periodic system, the so-called aluminium component, ifnecessary in the presence of such other materials as small quantities ofcompounds with free electron couples, for instance water, alcohol,oxygen pr Lewis bases or small amounts of multi-halogenated organiccompounds. By preference, a catalyst system is used has been formed bycombining vanadium and/or titanium compounds soluble in the solvent, forinstance vanadiumoxytrichloride and/or vanadiumtetrachloride and/ortitaniumtetrachloride and/or tetra-alkyltitanate with one or more,preferably organic, aluminium compounds, such as aluminiumtrialkyls,dialkylaluminiumhalide, and/or mono-alkylaluminiumhalide,dialkylaluminiummonohydride. Preference is given to application of thosealuminiumalkyl compounds which carry an alkyl group with 2 to 8 and,more particularly, with 2 to 5 carbon atoms.

Very good results are obtained with the combination ofvanadiumoxytrichloride and alkylaluminiumchloride, particularlyalkylaluminiumsesquichloride.

The ratio between the aluminium compound and the heavy-metal compoundmay be varied within wide limits, for instance between 2 : 1 and 500 :1, and preferably between 3 : 1 and 25 : 1. In a continuous embodimentof the process the catalyst components may be added directly - dissolvedin the distributor - to the polymerization zone.

The ethylene copolymers applicable according to the invention arecomposed of ethylene, at least one other alpha-alkene, and one or morepolyenes. For the other alpha-alkene any copolymerizable alpha-alkenemay be applied in the ethylene copolymer, but preferably those whichcontain 3 to 18 carbon atoms per molecule, and more particularly thosewhich contain 3 to 4 carbon atoms per molecule. Examples of applicablealpha-alkenes are butylene, 4-methylpentene-1, hexene, heptene, andhighly particularly propylene. Also mixtures of alpha-alkenes may beincorporated in the ethylene copolymers applicable according to theinvention, such as propylene and butylene. The ethylene content of theapplicable copolymers lies between 50 and 85 mol.-%. As a rule, ethylenecopolymers having the highest tack values will be found at an ethylenecontent of between 55 and 80 mol.-%, particularly between 60 and 77.5mol.-%.

The copolymerization reaction is usually effected at a temperature ofbetween -40° and 120° C., by preference between -20° and 80° C. Thepressure will as a rule amount to 1 to 50 atmospheres, but also higheror lower pressures may be applied. Preferably, the process is carriedout continuously. As solvent any liquid hydrocarbon compound may beapplied which is inert to the catalyst used and which, preferably, has 4to 18 carbon atoms per molecule. Examples of applicable hydrocarbons aresaturated aliphatic and cyclo-aliphatic hydrocarbons, like butane,pentane, cyclohexane, hexane, heptane or mineral oil fractions, aromatichydrocarbons, such as toluene and benzene, and halogenated organichydrocarbons, like tetrachloroethylene.

Such a temperature and pressure may be applied, to advantage, that oneor more of the monomers applied, particularly the alpha-alkene, such aspropylene, is in the liquid state and present in such a large quantitythat it acts as distributor. Another distributor will not be necessarythen.

In general, the molecular weight of the copolymers to be applied in theprocess according to the invention may be influenced by chainregulators, such as acetylene, hydrogen, butadiene-1,2,zincalkyls, andalkylhalides. By preference, hydrogen is applied as chain regulator. Themolecular weights of the rubber-like copolymers usually lie between5.10⁴ and 5.10⁶. Molecular weight is here understood to be theweight-average molecular weight as measured by means of thelight-scattering technique after removal of possibly present gel. Thebest tack values are reached if the molecular weight value lies between10⁵ and 10⁶.

The non-vulcanized mixtures of rubber-like copolymers, tackifying resin,and, possibly, additives should have a tensile strength of between 1.5and 50 kg/cm², preferably between 2.0 and 30 kg/cm², and particularlybetween 3 and 25 kg/cm². Optimum values are found at tensile strengthsbelow 15 kg/cm².

To be able to prepare mixtures having these tensile strength values oneshould start from rubber-like copolymers which, in the non-vulcanizedstate, already have some tensile strength, also called green strength.In view of, amongst others, the demand made on the elongation at break,said green strength of the undiluted polymer should not be too high.Good tensile strength values lie between 3 and 50 kg/cm², particularlybetween 5 and 35 kg/cm².

Rubber-like copolymers with a tensile strength of between 3 and 50kg/cm² generally have an ethylene content of between 50 and 80 mol.-% ofethylene. At higher ethylene contents the tensile strength increasesvery strongly. Tensile strengths of between 5 and 35 kg/cm², which areto be preferred, are usually found at ethylene contents of between 60and 77.5 mol.-% of ethylene. In general, the tensile strength willdecrease if the rubber-like copolymer is mixed with a tackifying resinand additives. However, with use of non-excessive quantities ofso-called reinforcing fillers, like carbon black, the tensile strengthcan be maintained at a high level and even be increased. Therefore, ifan amount of extender oil is applied, preference will be given toincorporate also an adapted quantity of reinforcing filler, particularlycarbon black, in the mixture in order to obtain the required tensilestrength. In this way, incorporation of considerable amounts ofadditives in the mixture is possible, e.g. a total of 200 parts to 100parts of rubber-like copolymer, whilst the tensile strength of themixture in the non-vulcanized state yet remains above 2 kg/cm². For oneskilled in the art it is possible by means of a few simple tests toestablish how large the quantities of additives to be applied may be inorder that the mixture continues to satisfy the demands made on thetensile strength.

Often, also the processing temperature may play a part in relation tothe tensile strengths to be achieved. Processing at temperatures of 100°C. and higher may cause the tensile strength to decrease.

As regards these additives allowance will also have to be made for thenecessity of keeping the elongation at break above 500%, preferablyabove 1700%, which is to be discussed below.

The tensile strength and the elongation at break are measured accordingto NEN 5602 (ring-method) at a rate of 10 cm/min. and a temperature of23° C. The thickness of the test rings amounted to 2 mm.

The mixtures of rubber-like copolymers, tackifying resins, and fillersapplied according to the process of the invention should show anelongation at break amounting to at least 500%, preferably at least800%, and highly particularly at least 1700%.

In the preparation of such mixtures, of course, copolymers should bestarted from which, already in the undiluted state, have a substantialelongation at break, for instance in excess of 625%, particularly inexcess of 1000%. The highest preference is for copolymers with anelongation at break of more than 1700%.

Copolymers showing these high values for the elongation at break can beprepared according to the processes known in the state of technique,which processes are mentioned elsewhere in this Application. Asufficiently high ethylene content should be provided then, i.e. anethylene content which usually exceeds 60 mol.-%, preferably exceeding65 mol.-%.

If the prepared copolymer with, for instance, 66 mol.-% of ethyleneshould show too low an elongation at break, said elongation at break canbe raised to the desired value by incorporation of more ethylene in thecopolymer.

Generally, it will not be possible to apply a copolymer whose ethylenecontent is greater than 85 mol.-% since the elongation at break stronglydecreases again at very high ethylene contents, even to below 625%.

By preference, therefore, copolymers are applied having an ethylenecontent of less than 80 mol.-%, particularly of less than 77.5 mol-%.

Because the elongation at break of mixtures of rubber-like copolymersand fillers as a rule decreases at an increasing filler content, oneshould be very careful that not too many fillers be incorporated in themixture. However, there are also copolymers which, even withconsiderable amounts of fillers, retain a high elongation value.Generally, these copolymers will show high ethylene contents. In thecase of these copolymers the phenomenon may even occur that theelongation at break of the mixture increases through the addition ofsmall quantities of fillers.

Also the phenomenon may occur that the elongation at break of copolymershaving high ethylene contents decreases very strongly after admixturewith fillers if processing takes place at lower temperatures, forinstance lower than 100° C. By increasing the processing temperature,one can avoid this strong decrease however.

With the aid of these guidelines it will be very well possible for oneskilled in the art to determine by means of a few simple tests whichmixtures are suitable for application according to the presentinvention.

Of course also mixtures of polymers can be used according to ourinvention provided that these mixtures show the necessary mechanicalproperties such as tensile strength and ultimate elongation at break.

Thus an ethylene-propylene-dienepolymer with high tensile strength(green-strength) can be mixed with an ethylene-propylenedienepolymerwith low tensile strength and the usual additives such as carbon blackand oil in order to obtain a mixture with a tensile strength lyingbetween 1.5 and 50 kg/cm² and an elongation at break of at least 500%.When such a mixture contains c ═ c bonds in the non-linear part of thepolymer chains with the structure as herebefore defined and the mixtureof polymer and tackifier is irradiated with light in the presence of asensitizer and oxygen excellent tack values can be obtained.

It is also possible to use mixtures of rubberlike polymers of ethylene,propylene and a non conjugated diene with other polymers such asrubberlike polymers of conjugated dienes especially butadiene orisoprene. Examples of these polymers are poly-butadienestyrene,polybutadienes, polyisoprenes, polybutadiene-acrylonitrilepolyisobutene-isoprene (butylrubber), and others.

These polymers have high molecular weights for instance in excess of10.000, preferably over 100.000.

The rubber-like copolymer of ethylene, at least one other alpha-alkene,and one or more polyenes should, by preference, have a thermogramrecorded by means of differential scanning calorimetry (dsc) at acooling rate of 8° C. per minute, in which the heat of crystallizationis plotted as a function of the temperature, which shows a maximum at atemperature between -7° and 11° C.

This is especially desirable if the rubber-like copolymer is preparedwith the aid of the catalyst combination vanadiumoxytrichloride andalkylaluminiumsesquichloride. Although high tack values are also foundwith application of other catalyst combinations if the peak in thedsc-thermogram lies at a temperature between -7° and 11° C., suitabletack values can also be found if the peak in the dsc-thermogram liesoutside said range, provided, of course, the demands made in relation tothe elongation at break and the tensile strength are satisfied.

The occurrence of a peak resulting from a heat effect at a certaintemperature in a thermogram recorded by means of differential scanningcalorimetry (a d.s.c. curve) indicates that a phase change occurs atthat temperature in the material examined. if, in recording d.s.c.curves of rubber-like ethylene copolymers, heated samples are startedfrom, and if these are cooled during the recording of the curves, a peakin the d.s.c. curve points to a change-over from a molten to acrystalline phase and, hence, to the existence of crystallites in theethylene copolymers examined.

In the case of the rubber-like ethylene copolymers examined by ApplicantX-ray diffraction patterns showed that the crystallites occurring inethylene propylene copolymers are built up of ethylene sequences.Reflections of polypropylene were not observed.

The temperature at which the crystallization peak occurs in the d.s.c.curve for rubber-like ethylene copolymers depends on the length of theethylene sequences and on the ethylene-sequential length distribution.Since the compositions based on ethylene copolymers and tackifiers yielda very high bonding strength if said compositions contain ethylenecopolymers that, in the d.s.c curve with a cooling rate of 8° C./min.,give a crystallization peak with a maximum at a temperature of between-7° and +11° C., preferably between -3° and +8° C., and moreparticularly between 0° and +6° C., it may be assumed that theoccurrence of tack is related to the occurrence of ethylene sequences ofa very specific length in these ethylene copolymers.

Applicant expects, although he does not want to be bound thereto, thatethylene copolymers are concerned here which behave analogously toethylene copolymers which have a sufficient number of ethylene sequenceswith 7 to 9 carbon atoms in the linear part to produce a d.s.c. curvehaving a peak with a maximum between -7° and +11° C.

The ethylene sequence lengths occurring in ethylene copolymers are,amongst others, dependent on the concentration of the comonomersincorporated in the ethylene copolymer and on the way in which thesecomonomers are included in the polymer. For instance, it is known thatthere are great differences in the kinetics of the copolymerization ofethylene and propylene with the various known polyenes, like1,4-hexadiene and dicyclopentadiene. The distribution of the comonomersin the ethylene copolymer differs for each catalyst system applied inthe preparation of the copolymers. For instance, in case of the sameincorporation of comonomers merely the variation of the catalyst systemmay cause the melting temperature of the crystallites present in thecopolymer to differ appreciably. Also catalyst additives like Lewisbases and halogenated activating compounds have influence on the meltingtemperature of the crystallites. In addition, also the polymerizationconditions, like pressure, temperature, polymerization time, solvent,and stirring intensity, are determinative with respect to the ethylenesequence length and the ethylene sequence length distribution occurringin the ethylene copolymer. It will be clear, therefore, that in the caseof a certain catalyst system only very special combinations ofpolymerization conditions and comonomer incorporation will yieldethylene copolymers which produce a crystallization peak with a maximumbetween -7° and 11° C. and which can be applied in the compositionsbased on ethylene copolymers and tackifiers with a high bondingstrength.

It will be clear from the above that a process for preparing theseethylene copolymers, which are applicable according to the invention,cannot be characterized merely on the basis of the comonomerincorporation and the catalyst system applied, because, in addition tothese factors, also the polymerization conditions are determinative withrespect to the ethylene sequence lengths occurring in the ethylenecopolymer formed. It has also appeared impossible to obtain a generalrelationship between the various polymerization parameters that are ofimportance and the position of the crystallization peak in the d.s.ccurve and, hence, the ethylene sequence length. Below, therefore, agenerally working method is described with the aid of which it will bepossible for one skilled in the art to prepare ethylene copolymersyielding a crystallization peak with a maximum lying at the requiredtemperature.

For each combination of catalyst system and polymerization conditionscan be determined in the following way how these ethylene copolymers canbe prepared. At a certain catalyst system and at chosen polymerizationconditions a series of batch-tests is conducted in which only theconcentration of comonomers in the monomer mixture to be polymerized,for instance that of the alpha-alkene, is varied. Subsequently, a d.s.c.curve is recorded for the ethylene copolymers so obtained. By variationof only the concentration of one of the comonomers, the ethylenesequence length and, hence, the temperature at which the maximum of thecrystallization peak occurs in these curves, will vary. Next, thecontent of incorporated comonomer of the ethylene copolymers obtained isdetermined, whereupon the temperature at which the maximum of thecrystallization peak occurs in the d.s.c. curve is plotted graphicallyagainst the content of comonomer built up in the ethylene polymer. Inthis way a relationship is obtained between the temperature at whichcrystallization of crystallites occurs in the ethylene copolymer and thecontent of incorporated comonomer. It may be assumed that at a 100%ethylene incorporation the crystallization will take place at about 130°C. (the crystallization temperature of polyethylene). The function soobtained is continuous; the area examined by Applicant could beconsidered linear for practical purposes. From this relationship can bederived at which concentration of incorporated comonomer, with thecatalyst system chosen, and under the reaction conditions chosen,rubber-like ethylene copolymers are obtained producing a crystallizationpeak in the d.s.c curve within the required temperature range.Realization of ethylene copolymers with such a comonomer content ispossible for one with average skill in the art. A method of this kind isapplicable for any catalyst system and for any combination ofpolymerization conditions.

The compositions according to the invention should contain one or moretackifing resins, so-called tackifiers. For tackifier any compound maybe applied in the compositions according to the invention which if addedto the ethylene copolymers increases the bonding strength of thesecopolymers. Organic cyclic resins containing at least one polarfunctional group and whose molecular weight amounts to at least 200 arehigh suitable. These resins may, for instance, be isoprenoid resins,terpenoid resins, phenol-aldehyde resins, phenol-acetylene resins oralkylated phenol resins.

Examples of well-applicable tackifiers are terpenes, compounds derivedfrom abietinic acid, pimaric acid, Diels-Alder reaction products ofisoprene with piperylene, butadiene, dicyclopentadiene or mixtures.Alkylated phenol resins may be applied to advantage, for instance theresins known by the trade names of `Amberol ST 140 F, Durez 19900, andResin 7521`. These tackifiers - which are given the highest preferencein the process of the present invention - belong to the group ofcondensation products of formaldehyde with alkyl phenol having amolecular weight of between 200 and 3000, particularly between 300 and2000, in which the alkyl group contains 1 to 30, more particularly 8 to12 carbon atoms. By preference, said alkyl group is highly branched.Examples of suitable alkyl groups are: 1,1,3,3-tetramethylbutyl,1,3,5-trimethylhexyl, and 1,3,5,7-tetramethyloctyl. Also modificationsof such resins may be applied, for instance the condensation products ofalkyl phenol with SCl₂ or S₂ Cl₂. Also mixtures of tackifiers may beapplied. In the compositions according to the invention the tackifiermay be applied in quantities of between 1 and 25% by weight, referred tothe ethylene copolymer, although, preferably, only relatively smallquantities, - in comparison with the state of technique - for instanceof 2 to 10% by weight, are applied.

The compositions according to the invention may also contain one or morevulcanizing agents. For vulcanizing agents in the composition accordingto the invention the usual vulcanizing agents may be applied, likesulphur and peroxides. The quantity of vulcanizing agent that may beincorporated in the compositions according to the invention may varywithin wide limits. As a rule, quantities are applied lying between 0.5and 5% by weight referred to the amount of ethylene copolymerincorporated in the composition; preferably, quantities of between 0.5and 2% by weight are applied. The compositions according to theinvention may also contain, besides vulcanizing agents, one or morevulcanization accelerators, such as zincdiethylcarbamate,tetramethylthiuramdisulphide, 2-mercaptobenzthiazole, and activatorslike diethyleneglycol. The rubber-like copolymers may be vulcanized inthe usual manner.

The compositions according to the invention may further contain theusual fillers and pigments. Examples of applicable fillers and pigmentsare carbon black, finely divided silica, precipitated chalk,precipitated aluminium silicate, magnesium silicate, titanium dioxide,and kaolin. Said substances are, as a rule, added in quantities lyingbetween 10 and 500, and more particularly between 25 and 250% by weight,referred to the amount of ethylene copolymer incorporated in thecompositions.

The compositions according to the invention may also contain oils. Saidoils may be naphthenic, paraffinic, as well as aromatic in character. Bypreference, aromatic oils are applied, since application of these oilsyields the highest bonding strengths. The aromatic content preferablyexceeds 40%. Most preference is for oils which when dissolved in hexanein a concentration of 0.74 g per liter show a transmission at 400 nm ofless than 70%. Usually, the oils are incorporated in the compositionsaccording to the invention in quantities of between 5 and 200% byweight, referred to the amount of rubber-like polymer incorporated inthe composition, preferably, however, in quantities of between 10 and100% by weight.

The tack values mentioned in this Patent Application have been measuredon a tack-meter developed by DSM, which meter is described in SGF Publ.no. 35: News on EPDM and general information of rubber technology.Briefly, the method described in this article comes to the following.

Strips of a certain shape are manufactured with the aid of a smallplunger-extruder with an electrically heated cylinder (100° C.).

These strips are subsequently exposed to light having a wave lengthbetween 200 and 800 nanometers. The strips are then carefully coveredwith aluminium foil, so that light can no longer influence them duringany subsequent storage at room temperature in a low-dust space. If thestrips are not covered they receive an extra amount of light whenstored, as a result of which there is a risk of the tack stronglyreducing or disappearing altogether. Following this period, a strip iswound on a cylinder which has previously been provided with adhesivetape, pointing outwards with its adhesive side. Subsequently, a secondwinding is applied to the first one, the second being ultimately pressedon the winding first applied. To this end the cylinder and the stripsapplied to it are given a constant peripheral speed of about 170 mm/min.and the strips are pressed together by pressing on a freely rotatablecylinder at a constant load of 1500 grams during one complete rotation.

After the strips have been pressed one time along the entirecircumference of the first cylinder the pressing cylinder is removed.Now the second winding is retained solely by tack. The width of thecontacting surface area between the first and the second winding amountsto 5 mm. After the second winding has been applied and after thepressure has been applied, the end of the second winding is connected toa draw bench and the force is measured - at room temperature - requiredto unwind the second rubber strip from the first one. In order to avoidthat the non-vulcanized, second rubber strip, which is connected to thedraw bench, starts stretching, the second winding and the clampingsection are provided with adhesive tape, the adhesive side of the tapepointing towards the rubber surface.

The unwinding speed has been defined at 1 cm/min. The unwinding lengthover which the tack is measured amounts to about 125 mm.

The d.s.c. curves described in the Patent Application have been recordedwith a differential scanning calorimeter marketed by Perkin Elmer underthe trade-mark of Perkin Elmer DSC 1 B, starting from ethylene copolymersamples of about 24 mg which, prior to the recording, were heated to100° C. The d.s.c. crystallization thermogram was recorded at a coolingrate of 8° C. per minute.

For the performance of the measurements mentioned in this PatentApplication, the temperature scale of the differential scanningcalorimeter had been calibrated with the aid of the following gaugesubstances: n-octane, norbornadiene, n-pentadecane, p-xylene,n-hexadecane, n-eicosane, n-tetracosane, pentaerythritoltetrastearate,n-octapentacositane, and indium. The melting temperatures obtained byheating these compounds at a rate of 8° C./min. were considered to beequal to the equilibrium temperatures. The purpose of the followingexamples is to explain the invention in more detail without limiting itin any way.

EXAMPLE I

A number of ethylene-propylene copolymers were prepared in hexane assolvent with the aid of a catalyst formed by combining VOCl₃ andethylaluminiumsesquichloride (SEAC). During the polymerizations thetemperature amounted to 36° to 42° C. and the reactor pressure was keptat a constant value of 2 ats g. The catalyst components were suppliedcontinuously in such a way that the VOCl₃ and SEAC concentrations in thereactor amounted, respectively, to 0.125 and 1.25mmoles per liter.

A mixture of propylene and ethylene was supplied in a volumetric ratiowhich, in the various experiments, varied from 0.71 to 1.05. After anaverage residence time in the reactor of 15 minutes the solution wastreated with hot water, in which the copolymer was recovered in the formof crumb. The results of these experiments are given in table I.

                  Table I                                                         ______________________________________                                               propylene            green   tack                                      No. of content    DSC       strength                                                                              value                                     test   % by w.    peak      kg/cm.sup.2                                                                           g/5 mm                                    ______________________________________                                        1      32         +13° C                                                                           22       60                                       2      33         +7° C                                                                            18      120                                       3      36         +1° C                                                                            4.5     1100                                      4      36         -2° C                                                                            2.5     700                                       5      37         -4° C                                                                            3       600                                       ______________________________________                                    

The tack values of these copolymers were determined of rubbercompositions prepared according to the following, general recipe:

    ______________________________________                                        polymer             100     parts by weight                                   zinc oxide          5                                                         stearic acid        1                                                         FEF carbon black    50                                                        Sundex 790*         40                                                        zincdibutyldithiocarbamate                                                                        2                                                         2-mercaptobenzthiazole                                                                            0.5                                                       tetramethylthiuramdisulphide                                                                      0.5                                                       sulphur             1.5                                                       Amberol ST 140 F**  5                                                         ______________________________________                                         *Aromatic oil marketed by Sun Oil, with a density of 0.979, an aniline        point of 117° F, and an aromatic content of 68.4 % by weight. This     aromatic oil contains a number of fractions that, partly, consist of          polynuclear aromatic compounds having a strongly photosensitizing action.     **A tackifier resin formed by polycondensation of a branched octyl phenol     and formaldehyde.                                                        

Of the compositions prepared strips were than made which were exposed totwo white fluorescence lamps of 20 Watts (type W 33) at a distance of 10cm for 4 hours. The maximum intensity of this light source amounted to205 μW per cm² per nm at 580 nm and to 64 μW at 480 nm. The total amountof radiated energy from the UV-light with a wave length of between 200and 400 nm amounted to the 16th part of the total quantity of radiatedenergy of the light in the wave length range from 200 to 600 nm. Thetotal amount of radiated energy received, which was supplied by theUV-light of 325 to 400 nm, amounted to the 14th part of the totalquantity of radiated energy of the light in the wave length range from325 to 600 nm.

After the exposure the tack measurements were conducted in the wayalready described. The results thereof are also mentioned in table I.

From these results it may be concluded that these copolymers show onlysmall tack values because the required C═C bonds are lacking.

EXAMPLE II

Copolymers of ethylene, propylene, and 5-ethylidenenorbornene-2 with adifferent dsc-peak temperature were mixed according to the recipe ofexample I.

Next, strips were made from these mixtures, which strips were carefullyscreened off from the light during a subsequent 24-hour storage period.

These strips were then subjected to tack measurements. The resultsthereof and the mechanical properties are given in table II.

                                      Table II                                    __________________________________________________________________________                 polymer, max.                                                                         polymer,                                                                            mixture,                                                                            mixture,                                                  tensile elongation                                                                          max. tensile                                                                        elongation                                   DSC peak                                                                             tack value                                                                          strength                                                                              at break                                                                            strength                                                                            at break                                     temperature                                                                          g/5 mm                                                                              kg/cm.sup.2                                                                           %     kg/cm.sup.2                                                                         %                                            __________________________________________________________________________    -18° C                                                                        250   >6.9    >1700 1.6    210                                         -16    220   1.8       430 1.4    120                                         -9      70   13.1     1340 --    --                                           -1     600   >3.5    >1400 --    --                                           +1     700   >19     >1700 3.0   1230                                         +2     890   >16.8   >1700 3.0   1160                                         +5     1175  35       1460 >6.4  >1700                                        +19    150   81        730 105   1040                                         __________________________________________________________________________

From these results appears that the highest bonding strength values arefound at dsc-peak temperatures of between -7° and +11° C., particularlyof between -3° and +8° C., if the light was carefully screened off. Thehighest tack value is reached at an elongation at break in excess of1700%. At tensile strengths in excess of 50 kg/cm² a low tack value isobtained.

EXAMPLE III

A copolymer of ethylene, propylene, and dicyclopentadiene was preparedaccording to the process of example I, on the understanding that thetemperature amounted to 35° C. and the propylene to ethylene ratio to1.05. The dicyclopentadiene concentration in the reactor was 22 mmolesper liter.

The polymer formed and the mixture prepared thereof had the followingcomposition and properties:

    ______________________________________                                        propylene content   34     % by weight                                        dicyclopantadiene content                                                                         5.8    % by weight                                        green strength      29     kg/cm.sup.2                                        elongation at break 840    %                                                  DSC peak            +3     ° C                                         tensile strength, mixture                                                                         4.5    kg/cm.sup.2                                        elongation at break, mixture                                                                      1350   %                                                  ______________________________________                                    

After preparation of a composition according to the recipe of example Iand the exposure of the strips with 2 fluorescence lamps (W 33) of 20Watts, also according to example I, a tack value was measured of 400 g/5mm.

From this result it is quite evident that copolymers containingdicyclopentadiene for third monomer show only low tack values.

EXAMPLE IV

The following compositions were prepared from anethylenepropylene-5-ethylidenenorbornene-2-copolymer - prepared in theway mentioned in example I - with a DSC peak temperature of +5° C., apropylene content of 28% by weight and a third monomer content of 9% byweight:

A. a composition was prepared according to example I, in which notackifier resin was applied however. The composition was exposed in theway described in example I.

B. four compositions were prepared according to the recipe of example I,whereupon they were exposed in different ways:

B1. one composition was exposed to a 2 × 20 W fluorescence light source(W 33, white) at a distance of 10 cm;

B2. one composition was exposed to a 2 × 20 W fluorescence light source(G 17, green) at a distance of 10 cm;

B3. one composition was exposed to a 2 × 20 W fluorescence light source(R 15, red) at a distance of 10 cm;

B4. one composition was kept carefully screened off from the light.

In the non-vulcanized state, the following properties were found:

    ______________________________________                                        tensile strength, polymer                                                                           35      kg/cm.sup.2                                     elongation at break, polymer                                                                        1460    %                                               tensile strength, mixture                                                                           >6.4    kg/cm.sup.2                                     elongation at break, mixture                                                                        >1700   %                                               ______________________________________                                    

The measured tack values (in g per 5 mm) are given in table III. Fromthese results appears that both a tackifier and exposure are necessaryto obtain high tack values.

It also appears from these results that only limited tack values can beobtained with the red light (with wave lengths above 600 mm). Althoughequally high tack values are achieved with the white and the greenlight, the white light produces these tack values at a slightly higherrate.

                  Table III                                                       ______________________________________                                                    A                                                                             no       B1      B2    B3    B4                                   time of exposure                                                                          tacki-   white   green red   no                                   hours       fier     light   light light light                                ______________________________________                                        1/2         --        2,800  --    --    --                                   1           --        8,000   1,200                                                                                800 --                                   2           260      16,000  10,000                                                                              1,000 600                                  4           260      15,400  15,600                                                                              1,100 600                                  5           --       --      --    --    600                                  6           --       15,800  16,100                                                                              --    --                                   16          --       --      --    1,400 --                                   18          160      16,800  15,200                                                                              --    700                                  24          --       0       12,000                                                                              --    --                                   30          --       0       0     --    --                                   ______________________________________                                         (--) not measured                                                        

EXAMPLE V

Of a number of ethylene-propylene-5-ethylidenenorbornene-2-copolymerscompositions were prepared according to the recipe of example I.

Exposure was effected with 4 fluorescence lamps of 40 W (W 33) at adistance of 1 meter for 6 hours.

The results were as follows:

    ______________________________________                                                                  elong-        elong-                                                 tensile  ation  tensile                                                                              ation                                 DSC-peak                                                                              tack     strength at break                                                                             strength                                                                             at break                              temp-   value    polymer  polymer                                                                              mixture                                                                              mixture                               erature g/5 mm   kg/cm.sup.2                                                                            %      kg/cm.sup.2                                                                          %                                     ______________________________________                                        -37° C                                                                         520      2.1        570  1.3     350                                  -18° C                                                                         520      >6.9     >1700  1.6     210                                   +2° C                                                                         4400     >16.8    >1700  3.0    1160                                   +5° C                                                                         8500     35        1460  >6.4   >1700                                 +19° C                                                                         480      81         730  105    1040                                  ______________________________________                                    

From these results the conclusion may be drawn that high tack values arereached if the mechanical properties satisfy the demands made and if theDSC peak lies in the temperature range from -7° to +11° C.

EXAMPLE VI

A copolymer as in example IV was started from, compositions beingprepared thereof according to the recipe of example I. The exposure wascarried out with an SP 500 mercury-vapour lamp yielding a maximum energyof over 5,000 μW per nm per cm² at 435 nm. The total light energybetween 325 and 400 nm amounted to 20% of the light energy between 325and 600 nm. The total light energy between 200 and 400 nm amounted to30% of the total quantity of light energy between 200 and 600 nm.

With the aid of filters it was seen to that in the one case the UV-lightwas filtered off below 325 nm and in the other below 395 nm.

The results of the tack measurements are mentioned in table IV. Fromthese results appears that it is advantageous to suppress the UV-light,although a certain amount may be tolerated without too stronglydisadvantageous effects resulting therefrom.

                  Table IV                                                        ______________________________________                                        time of exposure                                                                             light with    light with                                       in min.        γ>325 nm                                                                              γ>395 nm                                   ______________________________________                                        0                440 g/5 mm    440 g/5 mm                                     1                640          1,000                                           5                800          6,400                                           10              7,000        14,800                                           20             11,000        13,900                                           30              9,600        --                                               60             10,800        --                                               120            12,200        --                                               ______________________________________                                    

EXAMPLE VII

A mercury iodide lamp (HPI/T 375 W) was applied as light source in theexposure of a composition as in example VI. The maximum light energyamounted to 8,600 μW per nm per cm² at 540 nm at a distance of 15 cm.

The total light energy between 200 and 400 nm amounted to thetwenty-fifth part of the total light energy between 200 and 600 nm.

The total light energy between 325 and 400 nm amounted to the thirtiethpart of the total light energy between 325 and 600 nm.

The results of the tack measurements are mentioned in table V.

                  Table V                                                         ______________________________________                                        time of exposure  tack                                                        in sec.           in g/5 mm                                                   ______________________________________                                        0                   800                                                       60                 2,000                                                      1.5 × 60     5,400                                                      2 × 60      13,600                                                      5 × 60      13,600                                                      10 × 60     10,000                                                      20 × 60     10,400                                                      ______________________________________                                    

EXAMPLE VIII

In order to be able to make a comparison between the tack valuesobtained with the present invention and the tack values obtained withnatural rubber (natural rubber has of old been known for its good tack)and with SBR to which the Koresin tackifier usual for SBR has beenadded, the following two compositions were prepared:

    ______________________________________                                        NR (sheet I)    100         --                                                SBR 1500        --          100                                               Rhenacit .sup.1)                                                                              0.15        --                                                ZnO             3           3                                                 Stearic acid    2           2                                                 PBN .sup.2)     1           1                                                 PEF carbon black                                                                              50          50                                                Sundex 790      15          15                                                Koresin .sup.3) --          5                                                 Vulc. CZ .sup.4)                                                                              1.0         1.2                                               Sulphur         2.0         1.75                                              ______________________________________                                        The tack measured amounted in the case of: natural rubber to 2600 - 4600      g/5 mm, depending on the extent of decomposition on the roll,                 SBR to          600 g/5 mm.                                                    .sup.1) zinc salt of pentachlorothiophenol                                    .sup.2) phenyl -β-naphthylamine                                          .sup.3) condensation product of acetylene and tert. butyl phenol              .sup.4) conversion product of mercaptobenzthiazole and cyclohexylamine   

EXAMPLE IX

In order to investigate the influence of the temperature on the tack twocompositions were prepared according to example IV. The two compositionswere exposed in the way of example I, in which the one strip was kept at20° C. and the other was heated to 80°.

The results are given in table VI. From these results appears that hightack values are obtained more rapidly at an elevated temperature.

                  Table VI                                                        ______________________________________                                        tack value in g/5 mm                                                          time of exposure                                                              in hours                                                                              20° C          80° C                                    ______________________________________                                        0.5               2,000       3,000                                           1                 6,000       12,800                                          1.5               12,400      14,000                                          2                 18,800      16,400                                          ______________________________________                                    

EXAMPLE X

The influence of the storage time on the tack values was investigated bykeeping the mixture according to example IV B1 - which had been exposedfor 4 hours - shut off from the light and by measuring the tack at fixedintervals. The tack values are given in table VII.

                  Table VII                                                       ______________________________________                                        keeping-time          tack                                                    in weeks              g/5 nunm                                                0                     15,200                                                  2                     14,800                                                  3.5                   15,200                                                  5                     13,000                                                  9                     13,500                                                  ______________________________________                                    

These values show that the bonding strength hardly deteriorates as timepasses.

EXAMPLE XI

An ethylene-propylene-ethylidenenorbornene copolymer according toexample IV was mixed according to the recipe of example I.

Next, strips were made of this composition, which strips were submersedin a solution of 1.5 . 10⁻⁴ mol. tetraphenylporphyrin in 1 l. ofdichloromethane. The absorption after the sumbersion amounted to 300 mgof solution, i.e. 0.5 . 10⁻⁷ mol. per 30 cm².

Strips were also prepared whilst tetraphenylporphyrin had been includedin the mixing-recipe in that the photosensitizer had been included inthe oil beforehand. To every 100 g of rubber 2 . 10⁻⁴ respectively 4 .10⁻⁴ mol. of photosensitizer was admixed.

The exposure was effected as in example I.

The results of the tack measurements are given in table VIII.

                  Table VIII                                                      ______________________________________                                        tack value in g/5 mm                                                                submersed                                                                     in photo- 2.10.sup.-4 mol.                                                                         4.10.sup.-4 mol.                                   time of                                                                             sensiti-  photosen-  photosen-                                                                              without extra- -expos. zer sitizer sit                                        izer photo-                               in min.                                                                             solution  admixed    admixed  sensitizer                                ______________________________________                                              g/5 mm    g/5 mm     g/5 mm   g/5 mm                                    0     1,200     600        700      900                                       5     2,400     1,400      3,400    --                                        10    7,500     11,800     12,600   --                                        25    13,500    15,400     10,200   2,000                                     60    16,200    12,800     12,800   6,000                                     2 × 60                                                                        19,000    13,600     14,000   18,800                                    ______________________________________                                    

These results show that addition of extra sensitizer results in the timewithin which good tack values are obtained being considerably reduced.

EXAMPLE XII

Example XI was repeated, the exposure being effected with a mercuryiodide lamp (HPI/T 375 W). The light source used had a maximum intensityof 8600 μW per cm² per nm at 540 nm. The total quantity of radiatedenergy from the UV-light with a wave length of between 200 and 400 nmamounted to the twenty-fifth part of the total quantity of radiatedenergy of the light in the wave length range from 200 to 600 nm. Thetotal received amount of light energy supplied by the UV-light of 325 to400 nm amounted to the thirtieth part of the total quantity of radiatedenergy of the light from the wave length range from 325 to 600 nm.

Two mixtures were prepared at which 2 . 10⁻⁴ mol. tetraphenylporphyrinwere admixed per 100 g of rubber. In one of the mixtures no tackifierwas incorporated.

The results of the tack measurements are given in table IX.

                  Table IX                                                        ______________________________________                                                                         without                                      time of                                                                              with extra photo-                                                                          with extra photo-                                                                          extra photo-                                 exposure                                                                             sensitizer   sensitizer with                                                                            sensitizer                                   in sec.                                                                              without tackifier                                                                          tackifier    with tackifier                               ______________________________________                                        0      80 g/5 mm    800 g/5 mm   800                                          10     --            2,800       --                                           15     --            5,200       --                                           30     --            9,600       --                                           60     80            9,400        2,000                                       2 × 60                                                                         80            9,500       13,600                                       5 × 60                                                                         --           11,000       13,600                                       10 × 60                                                                        80           12,600       10,000                                       20 × 60                                                                        80           14,000       10,400                                       ______________________________________                                    

These results show that a tackifier is necessary to achieve tack. Italso appears that within a very short time high tack values can beobtained by making use of a mixture of sensitizers.

EXAMPLE XIII

A number of ethylene-propylene-ethylidenenorbornene copolymers wereprepared according to the process of example I. Compounding as well asirradiation were carried out according to the specifications of exampleI.

The properties of copolymers and of the mixtures prepared therefrom, aswell as the results of the tack measurements, are mentioned in table X.

                  Table X                                                         ______________________________________                                        polymer     I       II      III   IV     V                                    ______________________________________                                        propylene content,                                                                        34      30      29    28     28                                    % by w.                                                                      EN content, % by w.                                                                       4.2     5.9     6.8   8.2    5.4                                  DSC                                                                            temperature, ° C                                                                  +1      +3      +5    +5     +8.5                                 polymer tensile                                                                strength, kg/cm.sup.2                                                                    >13.4   >26.2   36    35     54                                   elongation- >1700reak, %                                                                          >1700   1400  1460   1060                                 mixture tensile                                                                strength, kg/cm.sup.2                                                                    >2.3    >5.1    >6.0  >6.4   38                                   elongation                                                                     at break, %                                                                              >1700   >1700   >1700 >1700  1480                                 tack value, g/5 mm                                                                        9400    10,400  13,200                                                                              >13,400                                                                              1620                                 ______________________________________                                    

The results of table X show that the tack value decreases rapidly as theDSC temperatures increase. It further appears that mixtures in whichcopolymers are incorporated which have the same propylene contents butdifferent DSC temperatures show greatly differing tack values. Itappears in addition that the tack value decreases rapidly if the tensilestrength of the mixture approaches the value of 50 kg/cm².

EXAMPLE XIV

Mixtures were prepared according to the recipe of example I, startingfrom the copolymer described in example IV, the only variation beingthat various tackifier resins were applied in a quantity of 5 parts per100 parts of copolymer.

All tackifiers were of the same type, viz. condensation products ofalkylphenol and formaldehyde with molecular weights within the range of500-2000.

The alkyl groups contained 8-12 carbon atoms and were strongly branched.

The mixtures were subsequently exposed in the way described in exampleI. The results of the tack measurements are mentioned in table XI.

                  Table XI                                                        ______________________________________                                                                   tack value                                         Tackifier                  g/5 mm                                             ______________________________________                                        I.     Amberol ST 140 F (Rohm & Haas, USA)                                                                   14,000                                         II.    Durez 19.900 (Hooker Chemicals, USA)                                                                  >14,000                                        III.   Resin 7521 (Rousselot S.A., Paris)                                                                    >10,000                                        ______________________________________                                    

These results show that tackifier I. may be replaced by tackifiers of adifferent origin without disadvantageous consequences.

EXAMPLE XV

Different types of oil were applied in the general mixing-recipe ofexample I, the copolymer described in example IX being applied.

The mixtures were also exposed for 4 hours according to the method ofexample I, whereupon the degree of the tack was determined.

The results are given in table XII.

                  Table XII                                                       ______________________________________                                                    aromatic content                                                                           percentage of                                                    in % by weight                                                                             transmission                                                                             tack                                                  according to at 400 nm  value                                     type of oil clay-gel method                                                                            %          g/5 mm                                    ______________________________________                                        paraffinic oil                                                                            0            100        320                                       451 HP Shellfex 68                                                                        25.6         100        320                                       Sunpar 150  14.1         100        340                                       Flexon 391  66.5         94         3600                                      Sundex 790  68.4         65         >15,000                                   Dutrex 55   78.2         65         >15,000                                   Sundex 8125 72.2         52         >15,000                                   ______________________________________                                    

These results show that the influence of the oil is extremely great.Decisive for the effect of the oil is the transmission measured at 400nm of a solution of 74 mg of oil in 100 ml of n-hexane in a 1-cmcuvette.

This transmission should be less than 100%, preferably however less than95%. The best results are obtained with oils showing a transmission ofless than 80%.

EXAMPLE XVI

In this example the influence is shown of a diamine anti-ozonant on theprovision of bonding strength. This type of anti-ozonant is known to becapable of suppressing singlet-oxygen reactions. To this end a mixturewas prepared and exposed at 20° C. in the way described in example IX.Also a second mixture was treated according to the process of exampleIX, the only difference being that the irradiation took place undernitrogen, as a result of which singlet-oxygen reactions were excluded.In the case of a third mixture, also 1 part ofN-cyclohexyl-N'phenyl-p-phenylene-diamine was admixed in the mixtureaccording to example IX per 100 parts of copolymer. The exposure tookplace in the same way as in example I.

The results are given in table XIII.

                  Table XIII                                                      ______________________________________                                        tack value, g/5 mm                                                                            exposure time, in hours                                                     0    1      2        4                                          ______________________________________                                        normal exposure 600    2450   >10,600                                                                              >15,000                                  exposure under N.sub.2                                                                        200    340    440    750                                      normal exposure, in the                                                       presence of 1 part of                                                         anti-ozonant    480    800    2,600  3,600                                    ______________________________________                                    

EXAMPLE XVII

In this example the influence is checked of increasing quantities offiller on the mechanical properties and the tack values of the mixture.The copolymer of example IV was for that purpose admixed and exposedaccording to example I (I). Also a mixture (II) was prepared in whichthe amount of carbon black was increased to 70 parts and the amount ofoil to 50 parts. A third mixture (III) was prepared in which 100 partsof carbon black and 70 parts of oil were applied. The results arementioned in table XIV below.

                  Table XIV                                                       ______________________________________                                               carbon         tack    tensile  elongation                             mixture                                                                              black   oil    value   strength at break                               ______________________________________                                        I      50      40     15,000  2.8 kg/cm.sup.2                                                                        >1700 %                                                      g/5 mm                                                  II     70      50     8,000   2.2      >1700                                  III    110     70     4,000   2.1      820                                    ______________________________________                                    

These results show that even with large amounts of carbon black and oilhigh tack values can be reached if the tensile strength and theelongation at break satisfy the demands made.

EXAMPLE XVIII

A copolymer of ethylene, propylene, and 5-ethylidenenorbornene-2, havinga DSC-peak temperature of +5.5° C., a tensile strength of 42 kg/cm², andan elongation at break of 1390% was admixed with additives according tothe recipe of example I, on the understanding that instead of 40 partsof Sundex 790 oil 30 parts of Sunpar 150 oil were applied. The mixturewas divided into two parts, 4.10⁻⁴ mol. of tetraphenylporphyrin beingadded to the one part and admixed. Next, the two mixtures were exposedfor 1 and 2 hours according to example I. For the sake of comparisonalso a test was conducted with application of 40 parts of Sundex 790.The mechanical properties of the mixtures showing no differences were asfollows: tensile strength in excess of 8.1 kg/cm² ; elongation at breaklarger than 1700%. The results of the tack measurements are mentioned intable XV.

                  Table XV                                                        ______________________________________                                        Mixture        tack after   tack after                                        with :         1 hour       2 hours                                           ______________________________________                                        Sunpar 150     250          400                                               Sunpar 150 and                                                                4.10.sup.-4 mol. of TFP                                                                      5800         3200                                              Sundex 790     --           >11,200                                           ______________________________________                                    

The results of table XV show that also paraffinic oils may be appliedprovided a photosensitizer is incorporated in the mixture.

EXAMPLE XIX

Copolymers were prepared from ethylene, propylene, and5-ethylidenenorbornene-2(EN) according to example I, on theunderstanding that for catalyst a mixture of diethylaluminiumchlorideand vanadiumoxytrichloride was applied.

The copolymer obtained had an ethylene content of 67.6 mol.-% and a DSCtemperature of -7° C. The EN content amounted to 5.1% by weight.Depending on the temperature at which the test plates were compressed,the tensile strength of the polymer amounted to 11.9 to 17.7 kg/cm², theelongation at break amounting to 880 to 1550%. In either case thehighest values were obtained at the highest compression temperature(140° C.). After admixture of the rubber-like copolymer with 50 parts ofcarbon black and 40 parts of oil according to the recipe of example I, atensile strength was reached of 24.6 kg/cm² and an elongation at breakof 140% if the mixing was carried out at 80° C. This mixture, afterhaving been exposed for 0, 2 and 4 hours according to example I, showedonly a very low tack value, respectively of 60, 100 and 100 g/5 mm. Ifthe mixture was prepared at a temperature of 140° C., whilst vulcanizingagents were left out of the mixture to avoid premature vulcanization,the tensile strength exceeded 6.5 kg/cm² and the elongation at breakexceeded 1700%. If the mixture was tested after exposure tack values of1100, >4600, and >5400 g/5 mm were found after exposure for,respectively, 4, 6, and 8 hours.

EXAMPLE XX

A copolymer was prepared according to example XIX, the ethylene contentof the product obtained amounting to 76.1 mol.-% and the EN content to5.1% by weight. The DSC temperature amounted to +21° C. The tensilestrength and the elongation at break of the polymer depended on thetemperature at which the test plates were prepared, see table XVI. Afterexposure according to the method of example I it was tried to measurethe tack. The tack value was so small that bonding did not occur at all.

                  Table XVI                                                       ______________________________________                                               80 ° C                                                                         80 ° C                                                                           140 ° C                                                                          140 ° C                                      tensile   elongation                                                                              tensile elongation                               compression                                                                            strength  at break  strength                                                                              at break                                 temperature                                                                            kg/cmn.sup.2                                                                            %         kg/cm.sup.2                                                                           %                                        ______________________________________                                        polymer  50        450       72      640                                      mixture  67        210       93      940                                      ______________________________________                                    

EXAMPLE XXI

In the way of example XIX, a copolymer was prepared with an ethylenecontent of 64.3 mol.-% of ethylene. The EN content amounted to 5.9% byweight, the DSC temperature to -12° C. the tensile strength of thepolymer amounted to 8.0 kg/cm², and the elongation at break to 1160%.After admixture with carbon black and oil according to example I, atensile strength was measured of 23 to 3.6 kg/cm² and an elongation atbreak of 130 to >1700%. The lowest tensile strength value and thehighest value for the elongation at break were found if the test plateshad been compressed at 160° C. If this polymer was subjected to theusual exposure according to example I a tack value was reached of >5200g/5 mm. The polymer mixture compressed at 80° C. (tensile strength 23kg/cm² and elongation at break 130%) showed very low tack values,respectively of 250 and 300 g/5 mm after exposure for 2 and 4 hours.These results clearly show that high tack values can be reached if themixtures satisfy the demands made on the tensile strength and theelongation at break.

EXAMPLE XXII

The following polymers were used. All polymers are copolymers ofethylene, propylene and ethylidenenorbornene (EN). From each polymer islisted:

a. the composition (weight percent ethylene, propylene and EN).

b. the mooney viscosity (ml × (1 + 4) 125° C.

c. dsc temperature

d. tensile strength and elongation at break of polymer

e. tensile strength and elongation at break when compounded according tothe compounding recepture in the application example 1.

    ______________________________________                                        Polymer A. Polymer B.  Polymer C.  Polymer D.                                 ______________________________________                                        a. 52, 38, 10                                                                            62, 28, 10  63, 28, 9   64, 31, 5                                  b. 68      59          58          54                                         c. not measurable                                                                        +4.5 ° C                                                                           +7 ° C                                                                             +7.5 ° C                            d. 2.7, 290 %                                                                            >3.2 >2365 %                                                                              44, 1800 %  47, 1350 %                                 e. 2.2, 270 %                                                                            3.3 >2365 % >4.2 >2365 %                                                                              14, 2290 %                                 Polymer E. Polymer F.  Polymer G.                                             a. 64, 26, 10                                                                            67, 28, 5   67, 25, 8                                              b. 71.5    54.5        75.5                                                   c. + 10 ° C                                                                       + 12 ° C                                                                           + 16 ° C                                        d. 47.5, 1110 %                                                                          54, 980 %   61, 730 %                                              e. 13.7, 2365 %                                                                          36, 1950 %  76, 1210 %                                             ______________________________________                                    

Mixtures were made of polymer A with each of the polymers B to G. Thecompound composition was according to the recepture of example 1 of theapplication.

    __________________________________________________________________________                tensile strength                                                                      elongation                                                                            tackvalue after                                   Polymer A.                                                                          Polymer B.                                                                          in kg/cm.sup.2                                                                        at break                                                                              4 hours w 33 ill.                                 __________________________________________________________________________     0    100   3.3     >2365   >15400                                            10    90    3.1     >2365   >9000                                             20    80    2.9     2160    >6400                                             30    70    2.9     1860    7000                                              40    60    2.8     960     3800                                              50    50    2.7     530     2200                                              60    40    2.6     280     1750                                              Polymer A.                                                                          Polymer C.                                                               0    100   >4.2    >2365   15000                                             10    90    3.4     >2365   19000                                             20    80    3.0     >2365   >15800                                            30    70    2.8     >2365   16000                                             40    60    2.8     1590    11200                                             50    50    3.0     660     3800                                              60    40    2.9     460     2200                                              70    30    2.8     290     1500                                              Polymer A.                                                                          Polymer D.                                                               0    100   14      2290    --                                                10    90    >11.3   >2365   4800                                              20    80    >9.1    >2365   >7600                                             30    70    4.2     >2365   >10400                                            40    60    3.3     >2365   11200                                             50    50    3.0     1530    6800                                              60    40    2.7     780     2600                                              70    30    2.7     320     1700                                              Polymer A.                                                                          Polymer E.                                                               0    100   >13.7   >2365   2200                                              10    90    >10.7   >2365   6000                                              20    80    >4.3    >2365   >14600                                            30    70    >3.9    >2365   >14400                                            40    60    3.1     >2365   >13600                                            50    50    2.9     1450    8400                                              60    40    2.9     1180    4200                                              70    30    2.8     410     2100                                              80    20    2.7     290     1400                                                          tensile strength                                                                      elongation                                                                            tackvalue after                                   Polymer A.                                                                          Polymer F.                                                                          in kg/cm.sup.2                                                                        at break                                                                              4 hours w 33 ill.                                 __________________________________________________________________________      0   100   36      1950    --                                                10    90    29      2150    --                                                20    80    17      2310    2000                                              30    70    >7.3    >2365   2100                                              40    60    >4.3    2365    >6200                                             50    50    3.0     2365    >7800                                             60    40    2.7     2365    >7400                                             70    30    2.6     550     3600                                              80    20    2.4     350     1800                                              Polymer A.                                                                          Polymer G.                                                               0    100   76      1210    --                                                10    90    67      1320    --                                                20    80    60      1400    --                                                30    70    43      1500    --                                                40    60    30      1580    --                                                50    50    21      1820    2100                                              60    40    11      1960    >7200                                             70    30    3.7     2260    >8400                                             80    20    3.0     540     1800                                              90    10    2.7     250     1350                                              __________________________________________________________________________

EXAMPLE XXIII

Mixtures were prepared from polymer B with polyisoprene (Cariflex IR305; cis 1.4 content: 92.0%, LVN 7.5 dl/g). These mixtures werecompounded according to the recepture given in example 1 of theapplication. With the exception that the oil content varied withpolyisoprene content.

    ______________________________________                                                         Mixture of  Mixture of                                                Poly-   70 parts PIP                                                                              50 parts PIP                                              isoprene                                                                              30 parts EPDM                                                                             50 parts EPDM                                             25 parts oil                                                                          32.5 parts oil                                                                            37.5 parts oil                                   ______________________________________                                        Polymer                                                                       tensile strength                                                                         1.5 kg/cm.sup.2                                                                         3.3 kg/cm.sup.2                                                                           14.5 kg/cm.sup.2                             elongation 750 %     2365 %      2365 %                                       Compound                                                                      tensile strength                                                                         0.9 kg/cm.sup.2                                                                         1.1 kg/cm.sup.2                                                                           1.6 kg/cm.sup.2                              elongation 110 %     2030 %      2070 %                                       Tack value 750       1200        4600                                         g/5 mm                                                                        after 6 hours                                                                 illumination with                                                             w 33/amp                                                                      ______________________________________                                    

EXAMPLE XXIV

Mixtures were made from polymer F and polyisoprene (Cariflex JR 305).

    ______________________________________                                                 60 parts polyisoprene                                                                      70 parts polyisoprene                                            40 parts EPDM                                                                              30 parts EPDM                                                    35 parts oil 32.5 parts oil                                          ______________________________________                                        Polymer                                                                       tensile strength                                                                         12.5 kg/cm.sup.2                                                                             4.5                                                 elongation 1050 %         990                                                 Compound                                                                      tensile strength                                                                         6.1 kg/cm.sup.2                                                                              1.4 kg/cm.sup.2                                     elongation 1650 %         1410 %                                              tack value after                                                                         3100 g/5 mm    1300 g/5 mm                                         6 hours illumina-                                                             tion with w 33                                                                lamp                                                                          ______________________________________                                    

EXAMPLE XXV

Mixtures from polymer B with a high cis polyisoprene (Natsyn 2200 cis1.4 content 96%) were made.

    ______________________________________                                                            30 parts polyisoprene                                              polyisoprene                                                                             70 parts EPDM                                                      25 parts oil                                                                             42.5 parts oil                                            ______________________________________                                        Polymer                                                                       tensile strength                                                                         1.6 kg/cm.sup.2                                                                            23.5 kg/cm.sup.2                                      elongation 200 %        2340 %                                                Compound                                                                      tensile strength                                                                         0.6 kg/cm.sup.2                                                                            2.4 kg/cm.sup.2                                       elongation 80 %         >2365 %                                               tack       600 g/5 mm   8000 g/5 mm                                           (after 4 hours                                                                illumination)                                                                 ______________________________________                                    

EXAMPLE XXVI

Mixtures of EPDM (polymer B) with SBR (SBR 1500) were made. Thecompounding was according to the recepture of example 1 of theapplication with the exception of the amount of oil.

    __________________________________________________________________________           Parts of                                                                      oil per                                                                       100 parts                                                                          Polymer     Compound                                                     of poly-                                                                           Tensile                                                                            Elong- Tensile                                               SBR    mer mix-                                                                           strength                                                                           ation  strength                                                                            Elongation                                      1500                                                                             EPDM                                                                              ture kg/cm.sup.2                                                                        %      kg/cm.sup.2                                                                         %      Tack                                     __________________________________________________________________________    100                                                                               0  25   19   390    1.2   260    650                                      50 50  371/2                                                                              >11  >2365  2.4   >2365  10800                                    40 60  40   >22  >2365  2.6   >2365  12600                                    30 70  421/2                                                                              31   2140   2.8   >2365  13800                                    20 80  45   34   1940   2.9   >2365  12000                                    10 90  471/2                                                                              33   2200   2.9   >2365  11000                                     0 100 50   >32  >2365  3.3   >2365  >15400                                   __________________________________________________________________________

Optimum values are achieved with 30 parts SBR. When EPDM with highergreen strength is mixed with SBR highest tack-values are reached athigher SBR contents.

EXAMPLE XXVII

A mixture of butylrubber (Butyl 218, Enjay) with EPDM-B was made. 80parts EPDM-B with 20 parts butylrubber were mixed, together withcompounding ingredients according to example 1 of the application exceptoil content that was 45 parts.

    ______________________________________                                                                       after                                                                         4 hours                                        Results:                       illumination                                   Polymer        Compound        Tack value                                     ______________________________________                                        tensile  elongation                                                                              tensile   elongation                                                                            g/5 mm                                   strength           strength                                                   22.5 kg/cm.sup.2                                                                       2190 %    2.9 kg/cm.sup.2                                                                         >2365 % 9800                                     ______________________________________                                    

What is claimed is:
 1. A process for preparing mixtures with buildingtack which are based on ( 1) a rubber-like copolymer of ethylene, atleast one other α-alkene, and one or more polyenes, and (2) a tackifyingresin, comprisingexposing said mixture in the presence of oxygen and acompound effective as a photosensitizer under the conditions of theprocess to an artificial light source radiating light at a wave lengthof between 200 and 800 nanometers, and imparting a radiated energy tothe mixture of at least 2 microwatts/cm² per nanometer; wherein saidmixture in the unvulcanized state and prior to said step of exposing, ischaracterized by an elongation at break of at least 500% and a tensilestrength of between 1.5 and 50 kg/cm² ; and wherein the copolymer ofsaid mixture contains C═C bonds in the non-linear part of the polymerchain, wherein the carbon atoms of said C═C bonds either (a) have twohydrocarbon groups which are in a vicinal cis relative position to eachother and which do not form part of the same system, or (b) have atleast three hydrocarbon groups attached thereto; and wherein saidcopolymer contains 50 to 85 mole % ethylene and 0.1 to 20% by weight ofsaid polyene; whereby said mixture is characterized by building tackafter said step of exposing.
 2. The process according to claim 1,wherein as a result of said step of exposing, said mixture is exposed toa total radiated energy of UV light of a wavelength of between 200 and400 nm which is at most half the total radiated energy of light in thewavelength range of from 200 to 600 nm.
 3. The process according toclaim 1, wherein, as a result of said step of exposing, said mixture isexposed to a total radiated energy of UV light of a wavelength of 200 to400 nm which is at most one fourth of the total radiated energy of lightin the wavelength ranging from 200 to 600 nm.
 4. The process accordingto claim 1, wherein, as a result of said step of exposing, said mixturereceives a total radiated energy of UV light of 325 to 400 nm, which isat most one fourth of the total radiated energy of light of wavelengthranging from 325 to 600 nm.
 5. The process according to claim 1,wherein, as a result of said step of exposing, said mixture is exposedto a total radiated energy of UV light of a wavelength of 325 to 400 nm,which is at most one sixth of the total radiated energy of light of thewavelength ranging from 325 to 600 nm.
 6. The process according to claim1, wherein said light is visible light.
 7. The process according toclaim 1, wherein the radiated energy exceeds 30 μW/cm² per nm.
 8. Theprocess according to claim 7, wherein said radiated energy exceeds 200μW/cm² per nm.
 9. The process according to claim 1, wherein said mixtureis exposed to a total radiated energy which is less than 15 Joules/cm²per nm.
 10. The process according to claim 1, wherein the tensilestrength of said mixture ranges between 2 and 30 kg/cm².
 11. The processaccording to claim 1, wherein said tensile strength ranges between 3 and25 kg/cm².
 12. The process according to claim 1, wherein said tensilestrength of said mixture is less than 15 kg/cm².
 13. The processaccording to claim 1, wherein said elongation at break of said mixtureexceeds 800%.
 14. The process according to claim 13, wherein saidelongation at break of said mixture exceeds 1700%.
 15. The processaccording to claim 1wherein said copolymer contains 55 to 80 mole %ethylene.
 16. The process according to claim 15, wherein said ethylenecontent is between 60 and 77.5 mole %.
 17. The process according toclaim 16, wherein said copolymer shows a peak at a temperature ofbetween -7° and 11° C., in a thermogram recorded by means ofdifferential scanning calorimetry at a cooling rate of 8° C. per minute,in which the heat of crystallization is plotted as a function of thetemperature.
 18. The process according to claim 17, wherein the peakoccurs between -3° and +8° C.
 19. The process according to claim 17,wherein the peak occurs between 0° and +6° C.
 20. The process accordingto claim 17, characterized in that the copolymer is prepared with theaid of the catalyst-combination vanadiumoxytrichloride andalkylaluminiumsesquichloride.
 21. The process according to claim 1,wherein said tackifying resin is prepared from an alkyl phenol andformaldehyde, said resin having a molecular weight of between 200 and3000, said alkyl group having 1 to 30 carbon atoms.
 22. The processaccording to claim 1, wherein said tackifying resin is prepared fromalkyl phenol and formaldehyde, said tackifying resin having a molecularweight of between 200 and 3000 and said alkyl group having 8 to 12carbon atoms.
 23. The process according to claim 1, wherein the amountof photosensitizer ranges between 0.001 to 1% by weight based on saidcopolymer.
 24. The process according to claim 23, wherein said quantityof photosensitizer ranges between 0.01 to 0.5% by weight.
 25. Theprocess according to claim 1, wherein said sensitizer comprises one ormore polynuclear aromatic compounds of 3 to 50 aromatic nuclei.
 26. Theprocess according to claim 1, wherein said photosensitizer is anaromatic oil, the aromatic content of which exceeds 40% by weight, saidaromatic oil having a transmission of less than 95% if 74 mg of said oilare dissolved in 100 ml of n-hexane.
 27. The process according to claim1, wherein said mixture comprises (i) and (ii) wherein(i) is a copolymerof ethylene, at least one other α-alkene and one or more polyenes, saidcopolymer having a tensile strength of at least 10 kg/cm² and anethylene content lying between 50 and 80 weight %, and (ii) is acopolymer of ethylene, at least one other α-alkene and one or morepolyenes with a tensile strength lower than 10 kg/cm² and an ethylenecontent lower than 65 weight %.
 28. The process according to claim 27,wherein the ethylene content of the copolymer of (i) lies between 62 and75 weight % and wherein the ethylene content of (ii) lies between 50 and63 weight %.
 29. The process according to claim 27, wherein each of (i)and (ii) has a Mooney viscosity ML(1 + 4)125° of at least
 20. 30. Theprocess according to claim 28, wherein each of (i) and (ii) has a Mooneyviscosity ML(1 + 4)125° of at least
 30. 31. A mixture prepared by theprocess of claim
 1. 32. The process of claim 1, wherein said polyene isethylidenenorbornene.
 33. The process of claim 15, wherein said polyeneis ethylidenenorbornene.